Most of the current project systems have single light source. Thus, to increasing the brightness of projected images, there is no much choice but to increase the illumination of a light source. In generally, the increase of illumination is achieved by employing light sources with higher power; however, a higher-power light source may result in a higher temperature, which may consequentially affect the light-emitting efficiency or even be detrimental to the light source lifespan. To overcome this issue, multi-light-source projection system is introduced in current market now. In a multi-light-source projection system, the lights generated by more than one light source are directed into one signal light-guiding rod first and then are mixed by the light-guiding rod thereby increasing the brightness of projected images. However, the lights emitted from the more than one light source may not have a certain homogenization and present a specific distribution characteristic (e.g., a Gaussian distribution); and conventionally, the light collection design for multi light sources are implemented as having their light-output directions toward the light-guiding rod only but without considering the specific light distribution. As a result, the light projected onto an image modulation device from a light-output end of the light-guiding rod may not be sufficiently homogenized, and accordingly the brightness of the projected image may have poor uniformity.